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Documents 2014/25

The population projections

Documentation of the BEFINN and BEFREG models

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This report documents how Statistics Norway (SSB) produces population projections using the BEFINN and BEFREG models.

This report documents how Statistics Norway (SSB) produces population projections using the BEFINN and BEFREG models. In BEFINN,
the population is projected by age and sex at the national level up to and including the year 2100. Immigrants from three
country groups of origin, Norwegian-born children with immigrant parents and the remaining general population are projected
as separate groups. In BEFREG, the population is projected by age and sex in 108 projection regions up to and including the
year 2040. The population is thereafter distributed to counties, municipalities and city districts in Oslo.

We use the cohort component method when projecting the population. This method requires two types of input:

• Updated figures for the population by sex and one-year age groups

• Assumptions about the future development of the demographic components

• fertility

• life expectancy

• domestic migration

• immigration

Most of the assumptions that are used in the cohort component method are stated as rates, probabilities or proportions by
sex and one-year age groups.

The results of a population projection depend to a great extent on which assumptions are used about the components. The assumptions
concerning future fertility, life expectancy, domestic migration and immigration are therefore produced in different alternatives:

• M – medium alternative

• H – high alternative

• L – low alternative

• K – constant alternative

• 0 – zero alternative

Altogether, SSB projects the population in 15 combinations of these M, L, H, K and 0 alternatives. Each alternative is described
using four letters in the following order: fertility, life expectancy, domestic migration and immigration. The term 'main
alternative' is used to designate the MMMM alternative, which indicates that the medium level has been used for all components.